# File lib/prawn/font/afm.rb, line 56
      def width_of(string, options={})
        scale = (options[:size] || size) / 1000.0

        if options[:kerning]
          strings, numbers = kern(string).partition { |e| e.is_a?(String) }
          total_kerning_offset = numbers.inject(0.0) { |s,r| s + r }
          (unscaled_width_of(strings.join) - total_kerning_offset) * scale
        else
          unscaled_width_of(string) * scale
        end
      end